The D-S action was first described just one year ago in arXiv0802.0864. Page 3 "...The reader might wonder at this point whether (6) is a discretization of a continuum action for GR, like Regge’s is a discretization of the Einstein-Hilbert action ∫√gR. We argue that this is the case, the continuum avatar of (6) being Plebanski’s action ." The most recent use of the new action was in December 2008, in the third of a series of papers by Rovelli and others, LQG propagator: III. The new vertex, arXiv0812.5018. Page 4 "...S (j, n) is the Regge action  of such a geometrical 4-simplex (more precisely, the Dittrich-Speziale action ), divided by 8π[itex]\hbar[/itex]GNewton ." More about this later. Speziale was one of Rovelli's students and then postdoc at Perimeter for several years ( http://www.perimeterinstitute.ca/personal/sspeziale/ ) and now fills a permanent faculty position at Marseille. Dittrich did her Diplomarbeit with Loll, was at Berlin or Potsdam for a while, postdoc at Perimeter, and is now at Utrecht. Trivia: since we say tetrahedron for 3-simplex, it would be correct to call the 4-simplex a pentachoron.